This invention relates to a core body of a bumper for attachment to a front of a vehicle such as an automobile.
A front bumper of an automobile generally serves to relax a shock to a driver or passenger and to prevent damages of the automobile body at a time of collision of the automobile with an object. A foamed polypropylene-based resin molding has been used as such a bumper core because of its excellent shock absorbing property and lightness in weight (JP-A-S58-221745 and JP-A-H11-334501).
The conventional front bumpers have been so constructed as to protect an automobile body when the automobile traveling at a speed of 4 or 8 km/hour collides with an object. With such a construction, however, pedestrians are likely to be seriously injured by collision with the bumper of an automobile. In particular, the bumper strikes the knee area of an adult pedestrian, which results in complex, unrecoverable fracture with permanent damage.
Thus, there is an increasing demand for a vehicle front bumper core which can protect a pedestrian on the occasion of collision with an automobile. More specifically, there is a need for a bumper core which can absorb energy of collision between the pedestrian and the automobile traveling at a relatively high speed of, for example, 40 km/hour, so that the leg impact can be reduced and serious knee injury can be avoided.
Even with the conventional bumper core constructions, it is possible to reduce the collision impact and to increase energy absorption by using a core material having a low compression modulus and a large volume. However, since the recent cars are designed to pursue energy saving and an increase of the inside occupation space, the bumper is required to be compact and to have a light weight. At present, no bumper cores on the market satisfy the above requirements at the same time.